| Popis: |
An implicit assumption in measures of ileal digestibility (ID) to estimate bioavailability of AA and N is that ID is not influenced by lower gut N metabolism. The absorption of nitrogenous compounds from the lower gut, derived from fermentative AA catabolism, may have an impact on N metabolism and microbial AA synthesis in the upper gut as a result of CO(NH(2))(2) recycling. The objective of this trial was to determine the apparent ID of N and AA in growing pigs fed a corn (Zea mays) starch and soybean (Glycine max) meal-based diet and receiving an infusion of N into the caecum at 40% of N intake. Eight pigs (initial BW of 23.3 ± 0.55 kg) were fitted with simple T-cannulas in the ileum and cecum and randomly assigned to 1 of 3 continuous cecal infusion treatments [saline, sodium caseinate, or CO(NH(2))(2)] according to a crossover design with 3 periods. Digesta samples were collected and pooled per pig for each 2-d period, freeze-dried, ground, and analyzed for DM, OM, total N, and AA. Lower gut N supply did not affect apparent ID of DM, OM, total N (85.4, 83.4, and 82.7 ± 1.74%; P = 0.31), or any AA (e.g., 90.1, 89.0, and 89.9 ± 1.08% for Lys; P = 0.70) for saline, casein, and CO(NH(2))(2) treatments, respectively. Apparent ID may be an insufficiently sensitive measure to determine effects of lower gut N metabolism on N absorption from the lower gut and subsequent recycling into the upper gut. |
